Typically, an external Digital Signal Processor (DSP) is used to perform a controlling function for a QAM modem. However, in order to perform a controlling function for the QAM modem externally, the external DSP controller has to sequentially pull all relevant processing data associated with the QAM modem control function from the QAM modem itself. Thus, it is a Master-Slave model, in which the DSP external controller is a Master device, and the QAM modem is a Slave device. The drawback to this Master-Slave model to control the QAM modem is a high latency of such QAM modem control due to insufficiently efficient physical interface of the external DSP (the Master device) with the QAM modem (the Slave device).
In addition, the prior art external DSP controller of a QAM modem makes the determination of whether a symbol loop of the QAM modem (or a carrier loop of the QAM modem) is locked by looking at all symbol loop parameters (or all carrier loop parameters respectively). This approach has a relatively high probability of a false lock.